Dual-gap magnetic flux responsive heads

ABSTRACT

In a dual-gap magnetic flux responsive head comprised of a saturable magnetic core with coils thereon and a pair of magnetic yokes forming a loop path for magnetic flux in connection with the core disposed therebetween and having dual gaps defined between one end of the core and the adjacent ends of the yokes; the core includes a first member having a lateral portion or crosspiece at one end from which a plurality of parallel, spacedapart legs integrally extend to receive the coils wound apart from the core, and a second member in the form of a crosspiece joined to the free end portions of the legs after the coils have been mounted on the latter.

360-119. XR 3,639,698 R EST AVAILABLE COPY 3639698 B Uemura et al. 51 Feb. 1, 1972 [54} DUAL-GAP MAGNETIC FLUX 2,931.864 4/1960 Moemring et al. ..l79/l00.2 C RESPONSXVE HEADS 3,150,358 9/l964 Newman et al. 179/1002 CF 3.239,823 3/1966 Chang ..346/74 MC 1 sebum Kanagawa-ken; Toyohlko 3,412,216 ll/l968 Rosado et 1. ..340/174.1 F

Fuse; Yosh1teka Hashimoto. both f Tokyo, all of Japan Primary Examiner-Bernard Konick 73 Assign; Sony Col-Putnam Tokyo Japan Assistant Examiner-Roberts. Tupper AttorneyLewis H. Eslinger, Alvin Sinderbrand and Curtis. [22] Med: NOV. 12, 1969 Morris & s ff [2H Appl. No.: 875,924

[57] ABSTRACT [30] Foreign Appucafian priomy Dam In a dual-gap magnetic flux responsive head comprised of a saturable magnetic core with coils thereon and a pair of mag- DCC. 28, Japan netic yokes i g a p p for magnetic flux in conncc tion with the core disposed therebetween and having dual gaps C. r between one end of the Core and the adjacent ends of CL i "gag/n4 F the yolces; the core includes a first member having a lateral [5 1 Search 52555 MC 2 portion or crosspicce at one end from which a plurality of parallel, spaced-apart legs integrally extend to receive the coils wound apart from the core. and a second member in the [56] Rekrem Cited form ota crosspieccjoincd to the free end portions of the legs UNITED STATES PATENTS after the coils have been mounted on the latter.

15 Claims, 15 Drawing Figures PATENIED EB I 872 BEST AVAILABLE COPY 3 6 a s ,6 9 a INVENTORS SABURO UEMURA TOYOHIKO FUSE YOSHITAKA HASHIMOTO 1 DUAL-GAP MAGNETIC rwx RESPONSIVE nexus This invention relates generally to magnetic flux rcspon heads, and more particularly to improvcmgnu in dugLgap magnetic flux responsive heads which are partlculfllly su for detecting a periodically alternating reference magnetization or signal recorded along a magnetic medium or sc member. as in a magnetic scaling system.

Magnetic flux responsive heads of the type to which this invention relates generally comprise a saturable magnetic core with plural coils thereon and a pair of yokes forming, in connection with the core disposed thercbctwecn, a l p P for magnetic flux, with dual gaps being defined between the opposites sides of one end portion of the core and the adjacent ends of the yokes. In an existing dual-gap magneti flu responsive head of the described ty e, the core is constituted by a one-piece core member for each coil, such core member consisting of relatively wide end portions and a relatively narrow leg portion extending integrally between the wide end portions. By reason of the above configuration of the core members, each coil must be wound directly on the leg portion core members are suitably joined together in side-by-side relation at their relatively wide end portions. However, since each core member is very small and a very slender conductive wire is employed for the coils, difficulties are encountered in winding the coils directly on the core members. Further, the winding of the coils directly on the respective core members has to be effected by hand, as automatic winding machines are not adapted for this operation. Thus, the manufacture of heads of the described type is costly, and further the winding by hand of the coils included in each head makes it difficult to provide such coils with uniform inductances, as is desired.

Accordingly, it is an object of this invention to provide dualgap magnetic flux responsive heads of the described type in which the above-mentioned defects and disadvantages of the described existing construction of the core are avoided.

Another object is to provide dual-gap magnetic flux responsive heads of the described type which can be efficiently and relatively inexpensively produced and assembled.

Still another object is to provide dual-gap magnetic flux responsive heads of the described type in which the plural coils of each head may be wound apart from the magnetic core, as on existing autontatic winding machines, so as to have exactly equal inductances. whereby to obtain a head having excellent performance characteristics.

In accordance with an aspect of this invention, in a dual-gap magnetic flux responsive head comprised of a saturable magnetic core with coils thereon and a pair of magnetic yokes forming, with the core disposed thcrebetween, a loop path for magnetic flux and having dual gaps defined between the opposite sides of one end portion of the core and the adjacent ends of the yokes; the core includes a first member having a lateral portion or crosspiece at one end from which a plurality of parallel, spaced-apart legs integrally extend to receive the coils wound apart from the core, and a second member in the form ofa cro'sspiece which isjoined to the free end portions of the legs only after the preformed coils have been mounted on the latter.

The above, and other objects, features and advantages of this invention, will be apparent in the following detailed description of illustrative embodiments of this invention which is to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a plan view of a duaLgap magnetic flux responsive head of the type to which this invention relates, but having a core ofexisting or conventional construction;

FIG. 2 is a sectional view taken along the line 22 on FIG. I, and showing the details of the conventional construction of the core;

FIG. 3 is a view similar to that of FIG. 2. but showing a core constructed in accordance with an embodiment of this invention;

BEST AVAILABLE COP FIG. 4 is an exploded elevational view showing the parts of the core illustrated on FIG. 3 and the coils which are wound apart from the core and assembled thereon;

FIG. 5 is a front elevational view of a dual-gap magnetic flux sensitive head according to this invention;

FIG. 6 is an elevational view of the.,.parts of a core in accordance with another embodiment of this invention, and showing, in broken lines, the coils assembled on such core;

FIG. 7 is an elevational view similar to that of FIG. 6, but with parts being partly broken away and showing another embodiment of this invention;

FIG. 8 is a sectional view taken along the line 8-8 on FIG.

FIG. 9 is a view similar to that of FIG. 6, but showing still another embodiment of the invention;

FIG. I0 is a view similar to that of FIG. 5, but showing a head including a core of the configuration shown on FIG. 9;

FIG. 11 is another view similar to that of FIG. 5, but showing a head in accordance with still another embodiment of this invention;

FIG. 12 is a plan view of the head illustrated by FIG. 11,

with one of the yokes of the head being shown partly broken away and in section;

FIGS. 13 and 14 are exploded perspective view of dual-gap magnetic flux responsive heads according to two additional embodiments of.this invention; and

FIG. I5 is a schematic diagram showing the manner in which two heads according to the embodiment of this invention illustrated by FIG. 14 may be connected in a magnetic scaling device or the like.

Referring to the drawings in detail, and initially to FIGS. I and 2 thereof, it will be seen that a dual-gap magnetic flux sensitive head I0 of the type to which this invention relates generally comprises a saturable magnetic core I] with two coils 12a and 12b thereon and a pair of magnetic yokes 13a and 13b. As shown, yokes 13a and 13b are of U-shapcd configuration and arranged in opposing relationship with core II therebetween so that ends 14a and 14b of yokes 13a and 13b abut and are suitably secured to opposite sides of one end portion of core I1 and the other ends 15a and 15b are adjacent to the other end portion of core II, but spaced therefrom, as by spacers 16a and 16b of a nonmagnetic material, such as, a nonmagnetic alloy of copper and beryllium or a suitable plastic resin.

As shown particularly on FIG. 2, the core 11 of a dual-gap magnetic flux responsive head of the described type has been heretofore conventionally constituted by a one-piece core member for each of the coils, for example, by core members 170 and 17b for the coils 12a and 1212, respectively, as shown. In such existing construction of the core, each of the core members 170 and 17b consists of relatively wide end portions 18 and I9 and a relatively narrow leg portion 20 extending integrally between the wide end portions 18 and I9 and on which the respective coil is to be disposed. By reason of the formation of the relatively wide end portions 18 and I9 integral with the leg portion 20 extending therebetween and intended toreceive the respective coil, it is apparent that such coil must be wound directly on the leg portion of its respective core member, whereupon two, as shown, or more of the core members 17a and 17b are suitably joined together in side-byside relation at their relatively wide end portions 18 and 19. However, the requirement that coils 12a and 12b be wound directly on core members [70 and 171; results in the manufacturing and functional disadvantages previously specified herein.

In accordance with the present invention. as shown on FIGS. 3 and 4, a saturable magnetic core III to be employed in place of the conventionally constructed core II in a dualgap magnetic flux responsive head of the described type may comprise a first member IZl having a lateral portion or crosspiece I19 at one end from which a plurality of parallel, spaced-apart legs a and 120k integrally extend, and a separately formed second member 118 in the form of a crosssrsrmmrr'cor piece which is suitablyjoined to the free end portions of legs 120a and 12% only after the coils 12a and 12b h been mounted on such legs. It will be apparent that, prior to the attachment of core member 118 to core member 121, coils 12a and 12b formed apart from the core 11, for example, on an existing coil-winding machine. may be slidably mounted on legs 120a and 12% over the free ends of the latter. The possibility of winding coils 12a and 12b on an automatic coil-windin machine greatly facilitates the manufacture of such coils and further makes possible the production of such coils with exactly equal inductances, as is desired. After core member 118 has been secured to core member 121 with the preformed coils 12a and 12b mounted on legs 120a and 120b, such C 111 is assembled between yokes 13a and 13!), with gap Spacers 16a and 1612 being provided, as previously described. a as shown on FIG. 5.

If desired, as shown on FIG. 6, a core 111 in accordan with this invention may have its core member 121' formed with a weblike extension 122 of its lateral portion 119' which projects between legs 120'a and 120'!) to act as a stop for positioning coils 12a and 12b along such legs. Similarly, core i member 118' may have a central extension 123 to project between the free end portions of legs 120'a and 120'b when member 118' is secured to the ends of the legs, and thus to act as a stop for positioning the coils.

The core constructed according to this invention may have its core member 118 secured to the end edges of legs 120a and 12011 of core member 121, in which case the core member 121 is given a length land the core member 118 is given a depth d (FIG. 4) selected so that l+d= the dimension L (FIG. 1) ofthe yokes 13a and 13b between which the core is disposed. Alternatively, as shown on FIGS. 7 and 8, a core 211 according to this invention may include a core member 221 having its length 1 equal to the dimension L of the yokes, in which case the core member in the form of a crosspiece may be in two parts 218a and 21817 which extend across, and are secured in facially abutting relation to the opposite sides of the free end portions of legs 220a and 2201) of core member 221. Further,

. as shown on FIGS. 7 and 8, spacers 16a and 16b may be attached to the opposite sides of the lateral portion 219 of core member 221 prior to the assembly of core 211 with yokes 13a and 13b. Thus, the spacers 16a and 16b are supported and reinforced by core portion 219 to prevent damage to the spacers during assembly of the head.

It is also to be noted with reference to FIGS. 7 and 8that the legs 220a and 22Gb of core member 221 may be reinforced, as by the attachment thereto of magnetic reinforcing strips 223 applied to the opposite sides of each leg between spacers 16a and 16b and crosspieces 218a and 2I8b.

The lateral portion 119 of core member 121 and the other core member or crosspiece 118 may both have a width w (FIG. 4) equal to the width W (FIG. 5) of yokes 13a and 13b or, as shown on FIG. 9, a core 311 according to this invention may have its crosspiece 318 only extended between, and secured to the free end portions of legs 320a and 32% of its core member 321 so that the width w at the end of core 311 having crosspiecc 318 is the distance between the outer edges of legs 320a and 3201) and is less than the width W of yokes 13a and 1317. Further, as shown on FIG. 9, if desired, the lateral portion 319 of core member 321 may also be of the reduced width w.

When core 311 has a width w at its ends smaller than the width W of the yokes, as shown on FIG. 10, the projection of yokes 13a and 13b laterally beyond core 311 shelter or shield the saturable magnetic core from undesired outside magnetic fluxes. However, if desired, shielding plates 324a and 324b of magnetic material (FIG. 10) may also be provided that are substantially coextensive with the lateral faces of yokes 13a and 13b and extend across the dual gaps and the core 311 therebetween with airspaces 325a and 325b being left between core 311 and the shielding plates. Such shielding plates 324a and 324!) further serve to shield core 311 from the effects ofextraneous or undesired outside magnetic fluxes.

Shielding of core 311 from extraneous or undesired outside magnetiC fluxes may be similarly achieved with the arrangement of FIGS. 11 and 12 in which the yokes 313a and 3131b are boxlike and have flanks 326a and 326b which are wrapped around core 311 and abut each other to completely envelop the core. Further, as shown, the gap spacers 316a and 3161: may have angled ends 327a and 327b which abut each other to space core 311 from the enveloping flanks 326a and 326b.

The dual-gap magnetic flux responsive heads having their cores constructed in accordance with the above-described embodiments of this invention may be used in connection with a magnetic medium or scale 28 (FIG. I) which may be rectilinear, as shown, or circular and is relatively movable with respect to the head in the direction of arrows 29, that is, across the face F of the head to which the dual gaps extend. Such magnetic medium or scale 28 has recorded along its length a periodically alternating reference magnetization or signal, as indicated at N-S-N-S, and the pitch P of such alternating magnetization is selected to be at least two times as large as the distancep between the centers ofthe gaps.

In place ofa magnetic medium or scale moved across a face of thehead, as described above, dual-gap magnetic flux responsive heads according to this invention may be provided to detect the periodically alternating magnetization on a rod which is enveloped by a head or heads and which is movable relative-to the latter. For example, as shown on FIG. 13, a head according to this invention may comprise a core 111 similar t'o'the core described with reference to FIGS. 3 and 4,

two coils 12a and 12b, gap spacers 16a and 16b and yokes 13a and 13b, with the lateral portion 119 of the core having an opening 29 therein and the spacers 16a and 16b and the yokes 13a and 13b having openings 30 and 31, respectively. extending therethrough in alignment with opening 29 to define a bore extending through the assembled head across the dual gaps of the latter. The head shown on FIG. 13 may be employed in connection with a rod 28' having the periodically alternating magnetization therealong and being longitudinally slidable in the mentioned bore constituted by openings 29, 30 and 31.

In accordance with another embodiment of this invention. as shown on FIG. 14, in place of the openings 29, 30 and 31 of the head of FIG. 13, the lateral portion 119 of core 111, the spacers 16a and 16b and the yokes 13a and 13b are respectively formed with aligned notches 29', 30 and 31' which, in the assembled head, cooperate to define .a groove extending across the dual gaps in the face of the head which is indicated at F on FIG. 1. A rod with periodically alternating magnetization as indicated at 28' on FIG. 13 may be slidably received in the mentioned groove of the head described with reference to FIG. 14. Further, as shown on FIG. 15, two of the heads H, and H, of the type described with reference to FIG. 14 may be assembled together with their faces F abutting and with the grooves in such faces registering to define a bore 32 in which the rod 28' is slidably received. Further, the dual gaps of head H, are, of course, registered with the dual gaps of head 11,.

When two heads according to this invention are employed: the circuit arrangement therefor may be as shown schematically on FIG. 15. In such circuit arrangement, the coils 12a and 12b of head H and the coils 12'a and l2'b of head H are excited by a conventional oscillator circuit 33 connected at one side to a terminal 34a and at its other side to parallel branches respectively extending through coils 12b and 12'a in series to a terminal 34b and through coils 12a and 12'b in series to a terminal 340, with the series-connected coils in each of these branches being arranged to obtain oppositely directed fluxes in the legs of the cores on which the coils are mounted. The terminals 34a, 34b and 34c may be connected to a conventional detecting circuit (not shown) which compares the output voltage across terminals 340 and 34b with the output voltage across terminals 340 and 34c. By employing two heads H, and H having their coils connected in series, as described, the output signals or voltages to be compared are twice as large as such signals would be if only a single dual-gap magnetic flux responsive head was employed.

Although illustrative embodiments of th invcmion have been described herein with reference to the drawings, it is to be understood that the invention is not limited to those precise embodiments. and that various changes and modifications may be effected therein by one Skilleddn the art without depaning from the scope or spirit of the invention.

What is claimed is:

1. In a dual-gap magnetic flux responsive head comprising a saturable magnetic core with a plurality of coils thereon and a pair of generally C-shaped magnetic yokes disposed at opposite sides of said core and forming, with said core disposed therebetween, a loop path for magnetic flux. the opposite sides of one end portion of said core and adjacent ends of said yokes being spaced from each other to define dual gaps therebetween; said core including a first member having a lateral portion at one end constituting an end portion of the core and a plurality of parallel. spaced-apart legs extending integrally from said lateral portion and receiving said coils which are prewound apart from said core, and a second core member in the form of a crosspiece formed separate from said first member and joined to free end portions of said legs following the mounting of said coils on the respective legs to constitute the other end portion of the core.

2. A dual-gap magnetic flux responsive head according to claim 1, in which the opposite end portions of said core constituted by said lateral portion of the first member and by said crosspiece are as wide as said yokes.

3. A dual-gap magnetic flux responsive head according to claim 1, in which at least one of said end portions of said core has a width substantially smaller than the width of said yokes.

4. A dual-gap magnetic flux responsive head according to claim 1. in which said second core member is secured to edges of said legs at the free ends of the latter and the combined length of said first and second core members, when thus secured. and measured in the direction between said end portions of the core, is equal to the corresponding dimension of said yokes.

S. A dual-gap magnetic flux responsive head according to claim 1, in which at least said first core member has an extension of said lateral portion projecting between said legs to act as a stop for locating said coils along said legs.

6. A dual-gap magnetic flux responsive head according to claim I, in which said first core member has a length in the direction of said legs equal to the corresponding dimension of said yokes, and said second core member includes two parts which extend across, and are secured in facially abutting relation to opposite surfaces of said free end portions of the legs which face toward said yokes.

7. A dual-gap magnetic flux responsive head according to LABLE BEST A 6 claim I, in which magnetic reinforcing strips are secured alon oppositely facing surfaces of each of said legs between said lateral portion of the first core member and said second Core member. I

8. A dual-gap magnetic flux responsive head according to claim I. in which nonmagnetic gap spacers are provided in said dual gaps.

9. A dual-gap magnetic flux responsive head according to claim 8, in which said lateral portion of the first core member has an opening therethrough and said gap spacers and yokes have openings therethrough aligned with said opening of the first core member to constitute a bore for slidably receiving a magnetic rod having periodically alternating magnetization recorded therealong to be detected by the head.

10. A dual-gap magnetic flux responsive head according to claim 1, in which adjacent surfaces of said lateral portion of the first core member, said gap spacers and said yokes have aligned notches defining a groove extending across the dual gaps in a face of the head constituted by said adjacent surfaces.

11. A dual-gap magnetic flux responsive head according to claim 10 in combination with a substantially identical head, and in which the two heads are in opposing relation with said face of one head abutting said face of the other head and with said dual zips and grooves of the heads registering so that the grooves e me a bore for sltdably receiving a magnetic rod having periodically alternating magnetization recorded therealong to be detected by the heads.

12. A dual-gap magnetic flux responsive head according to claim I, in which at least said one end portion of said core has a width substantially less than the width of said yokcs at said adjacent ends so that the latter project laterally beyond said one end portion of the core at said dual gaps to shield the core from undesired outside magnetic fluxes.

13. A dual-gap magnetic flux responsive head according to claim 12, in which shielding plates ofmagnetic material are attached to the opposite lateral faces of said yokes to enclose the latter and extend across said dual gaps and across said core between said gaps to further shield the core from said undesired outside magnetic fluxes.

M. A dual-gap magnetic flux responsive head according to claim 12, in which said yokes have lateral flanks which form sidewalls meeting outside of said core to envelop said core and further shield the latter from said undesired magnetic fluxes.

15. A dual-gap magnetic flux responsive head according to claim 14, in which nonmagnetic spacers are disposed in said gaps and have angled end portions extending toward each other between said one end portion of the core and said lateral flanks of the yokes.

new: 

1. In a dual-gap magnetic flux responsive head comprising a saturable magnetic core with a plurality of coils thereon and a pair of generally C-shaped magnetic yokes disposed at opposite sides of said core and forming, with said core disposed therebetween, a loop path for magnetic flux, the opposite sides of one end portion of said core and adjacent ends of said yokes being spaced from each other to define dual gaps therebetween; said core including a first member having a latEral portion at one end constituting an end portion of the core and a plurality of parallel, spaced-apart legs extending integrally from said lateral portion and receiving said coils which are prewound apart from said core, and a second core member in the form of a crosspiece formed separate from said first member and joined to free end portions of said legs following the mounting of said coils on the respective legs to constitute the other end portion of the core.
 2. A dual-gap magnetic flux responsive head according to claim 1, in which the opposite end portions of said core constituted by said lateral portion of the first member and by said crosspiece are as wide as said yokes.
 3. A dual-gap magnetic flux responsive head according to claim 1, in which at least one of said end portions of said core has a width substantially smaller than the width of said yokes.
 4. A dual-gap magnetic flux responsive head according to claim 1, in which said second core member is secured to edges of said legs at the free ends of the latter and the combined length of said first and second core members, when thus secured, and measured in the direction between said end portions of the core, is equal to the corresponding dimension of said yokes.
 5. A dual-gap magnetic flux responsive head according to claim 1, in which at least said first core member has an extension of said lateral portion projecting between said legs to act as a stop for locating said coils along said legs.
 6. A dual-gap magnetic flux responsive head according to claim 1, in which said first core member has a length in the direction of said legs equal to the corresponding dimension of said yokes, and said second core member includes two parts which extend across, and are secured in facially abutting relation to opposite surfaces of said free end portions of the legs which face toward said yokes.
 7. A dual-gap magnetic flux responsive head according to claim 1, in which magnetic reinforcing strips are secured along oppositely facing surfaces of each of said legs between said lateral portion of the first core member and said second core member.
 8. A dual-gap magnetic flux responsive head according to claim 1, in which nonmagnetic gap spacers are provided in said dual gaps.
 9. A dual-gap magnetic flux responsive head according to claim 8, in which said lateral portion of the first core member has an opening therethrough and said gap spacers and yokes have openings therethrough aligned with said opening of the first core member to constitute a bore for slidably receiving a magnetic rod having periodically alternating magnetization recorded therealong to be detected by the head.
 10. A dual-gap magnetic flux responsive head according to claim 1, in which adjacent surfaces of said lateral portion of the first core member, said gap spacers and said yokes have aligned notches defining a groove extending across the dual gaps in a face of the head constituted by said adjacent surfaces.
 11. A dual-gap magnetic flux responsive head according to claim 10 in combination with a substantially identical head, and in which the two heads are in opposing relation with said face of one head abutting said face of the other head and with said dual gaps and grooves of the heads registering so that the grooves define a bore for slidably receiving a magnetic rod having periodically alternating magnetization recorded therealong to be detected by the heads.
 12. A dual-gap magnetic flux responsive head according to claim 1, in which at least said one end portion of said core has a width substantially less than the width of said yokes at said adjacent ends so that the latter project laterally beyond said one end portion of the core at said dual gaps to shield the core from undesired outside magnetic fluxes.
 13. A dual-gap magnetic flux responsive head according to claim 12, in which shielding plates of magnetic material are attached to the opposite lateral faces of said yokes to eNclose the latter and extend across said dual gaps and across said core between said gaps to further shield the core from said undesired outside magnetic fluxes.
 14. A dual-gap magnetic flux responsive head according to claim 12, in which said yokes have lateral flanks which form sidewalls meeting outside of said core to envelop said core and further shield the latter from said undesired magnetic fluxes.
 15. A dual-gap magnetic flux responsive head according to claim 14, in which nonmagnetic spacers are disposed in said gaps and have angled end portions extending toward each other between said one end portion of the core and said lateral flanks of the yokes. 